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VIRAL ZOONOSES. ZOONOTIC VIRUSES TRANSMISSIBLE FROM ANIMALS ARTHROPODS often via a blood sucking arthropod VERTEBRATES bites, body fluids, inhalation etc. VIRAL ZOONOSES. PART I ARTHROPOD BORNE. transmission. arthropod vectors (blood sucking)

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viral zoonoses
VIRAL ZOONOSES
  • ZOONOTIC VIRUSES
    • TRANSMISSIBLE FROM ANIMALS
      • ARTHROPODS
        • often via a blood sucking arthropod
      • VERTEBRATES
        • bites, body fluids, inhalation etc
viral zoonoses1

VIRAL ZOONOSES

PART I

ARTHROPOD BORNE

transmission
transmission
  • arthropod vectors (blood sucking)
  • Many arboviral diseases world wide (hundreds)
slide5
ARBOVIRUSES
    • FEBRILE DISEASES
    • ENCEPHALITIS
    • HEMORRHAGIC FEVERS
arboviruses
ARBOVIRUSES

FAMILY

ENVELOPE

yes

yes

no

SYMMETRY

icosahedral

helical

icosahedral

GENOME

ssRNA (+ve)

ssRNA (-ve)

segmented

dsRNA,

segmented

slide7

Birds

Mammals

Humans

slide8
ARTHROPOD

Habitat

Diurnal activity

Preferred host

Annual activity

Overwintering ability

Transovarial transmission

VERTEBRATE

Migratory activity

Persistence of viremia

Clinical consequences

Reservoir ?

Dead end host?

prevention
PREVENTION
  • SURVEILLANCE
  • VECTOR CONTROL
  • REPELLENTS
  • CLOTHING
  • TIMING OF ACTIVITY (OR CANCELLATION)
  • VACCINE
sylvatic jungle cycle

vertebrate

arthropod

arthropod

vertebrate

human

SYLVATIC (JUNGLE) CYCLE
urban cycle

human

arthropod

arthropod

human

URBAN CYCLE

human cycle

note: viruses which have a human cycle may also have a sylvatic/jungle cycle

outbreaks
OUTBREAKS
  • TEND TO BE SUMMER/EARLY FALL
  • SPORADIC
  • UNPREDICTABLE
arboviral disease
ARBOVIRAL DISEASE
  • MANY DIFFERENT ARBOVIRUSES CAUSE DISEASE
  • OFTEN SUB-CLINICAL
arboviral disease1
ARBOVIRAL DISEASE
  • INITIAL VIRAL REPLICATION
    • endothelial cells
    • macrophages/monocyte lineage
  • INTERFERON (RNA VIRUSES)
    • headache, fever, myalgia
  • VIREMIA
    • spread to target tissues, depending on tropism of virus
recovery
RECOVERY
  • INTERFERON
  • CELL-MEDIATED IMMUNITY
  • ANTIBODY MAY PLAY A ROLE IN PREVENTING SPREAD DURING VIREMIC PHASE
diagnosis
DIAGNOSIS
  • Immunological techniques
  • RT-PCR for viral RNA
arbovirus encephalitis
ARBOVIRUS ENCEPHALITIS
  • SPORADIC
  • LOW % INFECTIONS -> CLINICAL CASES
  • NOT ALL CASES -> MAJOR DISEASE
  • PROBABLY UNDERDIAGNOSED
west nile virus
WEST NILE VIRUS
  • Reservoir: birds
  • Vector: mosquito
  • human, horse
    • dead end hosts

flavivirus

http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm

slide21

flavivirus

West Nile virus

west nile virus1
WEST NILE VIRUS
  • Symptoms:
    • Fever
    • Meningitis
    • Encephalitis

More rarely:

    • Acute flaccid paralysis
      • West Nile polio-like paralysis
        • poliomyelitis - inflammation spinal cord

flavivirus

http://www.cdc.gov/ncidod/dvbid/westnile/cycle.htm

west nile virus2
West Nile Virus

For every ~150 people infected

  • ~30 mild symptoms
    • mild fever, headache, body ache, maybe rash
      • may never see physician, even if do, may not be diagnosed
  • ~1 severe illness
    • e.g. encephalitis, meningitis, high fever, stiff neck, stupor, disorientation, coma, tremors, convulsions, muscle weakness
      • frequency of flaccid paralysis unknown, but much less than frequency of encephalitis

flavivirus

west nile virus3
WEST NILE VIRUS

Case fatality ratio:

  • Seen in all age groups but higher in the elderly
    • the majority of cases of neuroinvasive diseases and fatalities are over 50 yrs age
  • Transplant recipients may be at higher risk
    • increased incidence of clinical disease
    • increased risk of severe disease

flavivirus

slide26

http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv_transplant%20brochure6_12_07.pdfhttp://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv_transplant%20brochure6_12_07.pdf

west nile virus4
WEST NILE VIRUS

transmission:

  • Mosquito (vast majority of cases)
  • Blood transfusion (blood supply is now screened)
  • Organ donation

flavivirus

slide28

flavivirus

Reported Human WNV Disease Cases, US

1999 62

2000 21

2001 66

2002 4156

2003 9862

2004 2539

2005 3000

2006 4269

2007 3630

2008 1338

2009 515 (as of 10-20-09)

2008 Case Fatality Rate = 44/1356 = 3.2%

st louis encephalitis
ST. LOUIS ENCEPHALITIS
  • Second commonest mosquito borne disease in US
  • Reservoir: birds
    • Man is usually a dead end host
  • Vector: mosquito
  • <1% infections clinical
  • Elderly at higher risk
  • CFR 3-25%
  • ~100 cases/year av.

flavivirus

eastern equine encephalitis
EASTERN EQUINE ENCEPHALITIS
  • Reservoir: birds
  • Vector: mosquito
  • Sentinels
    • horse,quail, turkey
  • Under 15yrs, over 50yrs at higher risk
  • CFR ~35%
  • ~5 cases/year av.
  • horses and humans dead end hosts

CDC

togavirus

western equine encepalitis
WESTERN EQUINE ENCEPALITIS
  • Reservoir: birds
  • Vector: mosquito
  • Sentinels
    • horse,quail, turkey
  • Children at higher risk
  • CFR 3-5%
  • humans and horses dead end hosts

USA: last confirmed human case 1999

togavirus

california serogroup encephalitis includes la crosse virus
CALIFORNIA SEROGROUP ENCEPHALITIS(includes La Crosse virus)
  • Recently commoner in eastern US
  • Reservoir: small mammals
  • Vector: mosquitos
  • Children at higher risk
  • Low CFR
  • ~80 cases/year av.

bunyavirus

slide34

bunyavirus

2000 - 2 cases in SC, Charleston area

La Crosse life cycle

arboviruses fever and hemorrhagic fever
ARBOVIRUSES – FEVER AND HEMORRHAGIC FEVER

FAMILY

FLAVIVIRIDAE

Dengue

Yellow fever

REOVIRIDAE

Colorado tick fever

MAIN DISEASES

fever, hemorrhagic fever

hemorrhagic fever

fever

DISTRIBUTION

World wide,

especially tropics

Africa, S. and C. America

North America

colorado tick fever coltivirus
COLORADO TICK FEVER- coltivirus

Vector: tick

  • Mild disease in man
  • Fever, rash, arthralgia
  • RMSF important consideration in differential diagnosis
  • Probably common, rarely reported

Reovirus family

dengue fever

flavivirus

DENGUE FEVER
  • jungle cycle (monkeys-mosquitoes)
  • urban cycle (man-mosquitoes)
  • rapidly increasing disease in tropics
  • approx. 100-200 cases/yr in US due to import
    • occasional indigenous transmission
  • 50-100 million cases per year worldwide
    • ~900,000 cases in Central and S. America in 2007
slide39

flavivirus

http://news.bbc.co.uk/2/hi/americas/6422319.stm

patients being treated for Dengue fever in a Paraguayan hospital

dengue fever1

flavivirus

DENGUE FEVER
  • Fever (overlaps with viremic phase)
  • headache
  • retro-orbital pain
  • myalgia, arthralgia
  • severe joint and muscle pain ‘breakbone fever’
  • sometimes rash
  • may look like flu, measles, rubella
  • more rarely encephalitis
dengue hemorrhagic fever dengue shock syndrome

flavivirus

DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME
  • hemorrhages
  • plasma leakage
  • hemoconcentration
  • hypotension
  • circulatory failure
  • shock
slide42

flavivirus

CDC

DHF - petechiae

slide43

Dengue hemorrhagic fever - pleural effusion

CDC

Vaughn DW et al. J Infect Dis 1997; 176:322-30.

dengue hemorrhagic fever

flavivirus

DENGUE HEMORRHAGIC FEVER
  • immunopathological
  • 4 serotypes (1, 2, 3, 4)
    • increase in areas in which all 4 circulate has led to more cases DHF fever in South and Central America
    • Entomologic, serologic and virologic conditions are now such that locally acquired DHF can occur in South Texas
  • maternal antibody
dengue hemorrhagic fever1

flavivirus

DENGUE HEMORRHAGIC FEVER
  • Immune enhancement hypothesis
    • more mononuclear cells infected
    • infected monocytes release vasoactive mediators
    • increased vascular permeability
    • hemorrhagic symptoms
dengue hemorrhagic fever2

flavivirus

DENGUE HEMORRHAGIC FEVER
  • do not give aspirin, ibuprofen
    • because of anticoagulant affects
    • (acetaminophen OK)
  • children more severe disease
  • CFR depends on rapid response
    • can be as low as 1%
yellow fever

flavivirus

YELLOW FEVER
  • jungle and urban cycles
  • hemorrhages
  • degeneration liver, kidney, heart
  • CFR 50%
  • Vaccine (live attenuated)
    • important to consider in travel to areas with yellow fever
    • egg grown
    • contraindicated in immune suppression

CDC

last yellow fever epidemic in US - 1905

west nile virus5
WEST NILE VIRUS

flavivirus

west nile virus6

SC

WEST NILE VIRUS

Case fatality ratio:

  • Higher in elderly
      • The 1 fatality in SC in 2005 was over 65 years old
  • Peaks about Aug-Sept

SC - 2005

flavivirus

http://westnilemaps.usgs.gov/sc_human.html

slide56

1999

West Nile virus

slide57

2000

West Nile virus

slide58

2001

West Nile virus

slide59

2002

West Nile virus

slide60

2003

West Nile virus

slide61

2004

West Nile virus

slide62

2005

West Nile virus

slide63

2006

West Nile virus